There exist at present on the market two kinds of coffee making machines, one using ground coffee, the other prepackaged cakes of coffee.
In the first case, the ground coffee is disposed in a filter of cylindrical shape, mounted on a filter-carrying cup, fixed pivotally in a bayonet system with helicoidal ramps, located below the cup carrier, whilst ensuring, at the end of the path of movement, the squeezing of a joint, called a cup joint, fitted below the cup carrier such that the hot water cannot escape laterally.
The document DE-A-573.054 has for its object a percolation device adapted to coact with an apparatus for the infusion of coffee by means of a connection, so as to prepare coffee-based beverages in small or large quantities; this device is characterized by the fact that a small or large dish, which comprises a sealed bell, is articulated relative to a pivot carried by the connection, itself provided with a sealing packing.
This earlier document defines the state of the art but is unsuitable for use with cakes containing coffee.
In the second case, on the other hand, the use of prepackaged cakes of coffee requires the use of a filter-carrying cup specially designed for this purpose. To obtain the infusion, the filter-carrying cup, on which the cake is disposed, is introduced into a cylindrical recess comprising throats in the form of helicoidal ramps, specially adapted to the filter-carrying cup. Each ramp is open and permits the introduction of the cup according to a limited angular position. The cake of coffee is encased between two sheets of paper, permeable to liquids, welded together forming a collar useful for gripping the cake of coffee after its infusion.
In known devices of this type, the collar of the prepackaged cake of coffee comprises an extra thickness and renders difficult the introduction of the filter-carrying cup into its cylindrical recess. When the infusion of the coffee is finished, and the filter-carrying cup is withdrawn from its recess, it often happens that the infused cake of coffee remains behind, because its edges bear against the walls of the cylindrical recess and in the helicoidal throats.
Under these circumstances, the user manually picks out the infused cake of coffee at the risk of burning himself, because the cylindrical recess is then at a temperature of about 90.degree. C.
Solutions have been proposed to overcome these drawbacks, by using devices specially designed for this purpose.
There are already known different means permitting using a conventional coffee making machine for the infusion of cakes or tablets of prepackaged coffee, such as those described in the patents DE-A-573 054 and EP-A-0 070 403. An adapter, designed to be secured below the hot water dispenser of the machine, in place of the original filter-carrying cup, comprises at its base devices permitting the mounting by a bayonet system of a filter-carrying cup corresponding to that used in machines for prepackaged cakes of coffee.
Such a solution, which requires having recourse to the juxtaposition of subassemblies of different commercial origin, in addition to the fact that it does not facilitate the use of prepackaged cakes of coffee in conventional coffee machines, renders the latter less useful; and in addition it does not resolve the problem raised by the extraction after infusion of the cakes soaked with boiling water.
The document EP-A-0 555 775 provides a sliding system provided with a receptacle with a filter for an espresso coffee making machine, which comprises a cylindrical body with inclined annular surfaces, provided with a handle, the cylindrical body being adapted to turn to raise or lower itself on corresponding inclined surfaces of a structure of box shape. During raising, the cylindrical body raises the receptacle with its filter, without rotation, against a fixed structure, which it faces, said receptacle being thus subjected to a linear movement without rotation. The fixed structure is a toric joint, provided with a lower circular groove and an upper circular groove for better sealing, at the upper edge of the receptacle.
The system for raising or lowering the cylindrical body uses the coaction of several surfaces having inclined surfaces. In addition to problems of production and the cost of production, there is the possibility of very strong gripping during these rising and falling movements; moreover, the introduction of said cylindrical body into the box-shaped structure is not easy.